One way transparent display

ABSTRACT

A transparent emissive device is provided. The device may include one or more OLEDs having an anode, a cathode, and an organic emissive layer disposed between the anode and the cathode. In some configurations, the OLEDs may be non-transparent. The device may also include one or more locally transparent regions, which, in combination with the non-transparent OLEDs, provides an overall device transparency of 5% or more.

This application is a continuation of U.S. application Ser. No.17/183,582, filed Feb. 24, 2021, which is a divisional of U.S.application Ser. No. 16/382,281, filed Apr. 12, 2019, which is adivisional of U.S. application Ser. No. 15/170,986, filed Jun. 2, 2016,which is a divisional of U.S. Application Ser. No. 13/656,188, filedOct. 19, 2012, and is related to U.S. application Ser. No. 13/912,961,filed Jun. 7, 2013, which is a continuation-in-part of U.S. ApplicationSer. No. 13/656,188, filed Oct. 19, 2012, and is also related to U.S.application Ser. No. 14/049,468, filed Oct. 9, 2013, which is acontinuation-in-part of U.S. Application Ser. No. 13/656,188, filed Oct.19, 2012, the disclosure of each of which are incorporated by referencein their entirety.

The claimed invention was made by, on behalf of, and/or in connectionwith one or more of the following parties to a joint universitycorporation research agreement: Regents of the University of Michigan,Princeton University, The University of Southern California, and theUniversal Display Corporation. The agreement was in effect on and beforethe date the claimed invention was made, and the claimed invention wasmade as a result of activities undertaken within the scope of theagreement.

FIELD OF THE INVENTION

The present invention relates to OLEDs and, more specifically, to OLEDdevices that are transparent and emit light primarily or entirelythrough a single surface.

BACKGROUND

Opto-electronic devices that make use of organic materials are becomingincreasingly desirable for a number of reasons. Many of the materialsused to make such devices are relatively inexpensive, so organicopto-electronic devices have the potential for cost advantages overinorganic devices. In addition, the inherent properties of organicmaterials, such as their flexibility, may make them well suited forparticular applications such as fabrication on a flexible substrate.Examples of organic opto-electronic devices include organic lightemitting devices (OLEDs), organic phototransistors, organic photovoltaiccells, and organic photodetectors. For OLEDs, the organic materials mayhave performance advantages over conventional materials. For example,the wavelength at which an organic emissive layer emits light maygenerally be readily tuned with appropriate dopants.

OLEDs make use of thin organic films that emit light when voltage isapplied across the device. OLEDs are becoming an increasinglyinteresting technology for use in applications such as flat paneldisplays, illumination, and backlighting. Several OLED materials andconfigurations are described in U.S. Pat. Nos. 5,844,363, 6,303,238, and5,707,745, which are incorporated herein by reference in their entirety.

One application for phosphorescent emissive molecules is a full colordisplay. Industry standards for such a display call for pixels adaptedto emit particular colors, referred to as “saturated” colors. Inparticular, these standards call for saturated red, green, and bluepixels. Color may be measured using CIE coordinates, which are wellknown to the art.

One example of a green emissive molecule is tris(2-phenylpyridine)iridium, denoted Ir(ppy)3, which has the following structure:

In this, and later figures herein, we depict the dative bond fromnitrogen to metal (here, Ir) as a straight line.

As used herein, the term “organic” includes polymeric materials as wellas small molecule organic materials that may be used to fabricateorganic opto-electronic devices. “Small molecule” refers to any organicmaterial that is not a polymer, and “small molecules” may actually bequite large. Small molecules may include repeat units in somecircumstances. For example, using a long chain alkyl group as asubstituent does not remove a molecule from the “small molecule” class.Small molecules may also be incorporated into polymers, for example as apendent group on a polymer backbone or as a part of the backbone. Smallmolecules may also serve as the core moiety of a dendrimer, whichconsists of a series of chemical shells built on the core moiety. Thecore moiety of a dendrimer may be a fluorescent or phosphorescent smallmolecule emitter. A dendrimer may be a “small molecule,” and it isbelieved that all dendrimers currently used in the field of OLEDs aresmall molecules.

As used herein, “top” means furthest away from the substrate, while“bottom” means closest to the substrate. Where a first layer isdescribed as “disposed over” a second layer, the first layer is disposedfurther away from substrate. There may be other layers between the firstand second layer, unless it is specified that the first layer is “incontact with” the second layer. For example, a cathode may be describedas “disposed over” an anode, even though there are various organiclayers in between.

As used herein, “solution processible” means capable of being dissolved,dispersed, or transported in and/or deposited from a liquid medium,either in solution or suspension form.

A ligand may be referred to as “photoactive” when it is believed thatthe ligand directly contributes to the photoactive properties of anemissive material. A ligand may be referred to as “ancillary” when it isbelieved that the ligand does not contribute to the photoactiveproperties of an emissive material, although an ancillary ligand mayalter the properties of a photoactive ligand.

As used herein, and as would be generally understood by one skilled inthe art, a first “Highest Occupied Molecular Orbital” (HOMO) or “LowestUnoccupied Molecular Orbital” (LUMO) energy level is “greater than” or“higher than” a second HOMO or LUMO energy level if the first energylevel is closer to the vacuum energy level. Since ionization potentials(IP) are measured as a negative energy relative to a vacuum level, ahigher HOMO energy level corresponds to an IP having a smaller absolutevalue (an IP that is less negative). Similarly, a higher LUMO energylevel corresponds to an electron affinity (EA) having a smaller absolutevalue (an EA that is less negative). On a conventional energy leveldiagram, with the vacuum level at the top, the LUMO energy level of amaterial is higher than the HOMO energy level of the same material. A“higher” HOMO or LUMO energy level appears closer to the top of such adiagram than a “lower” HOMO or LUMO energy level.

As used herein, and as would be generally understood by one skilled inthe art, a first work function is “greater than” or “higher than” asecond work function if the first work function has a higher absolutevalue. Because work functions are generally measured as negative numbersrelative to vacuum level, this means that a “higher” work function ismore negative. On a conventional energy level diagram, with the vacuumlevel at the top, a “higher” work function is illustrated as furtheraway from the vacuum level in the downward direction. Thus, thedefinitions of HOMO and LUMO energy levels follow a different conventionthan work functions.

More details on OLEDs, and the definitions described above, can be foundin U.S. Pat. No. 7,279,704, which is incorporated herein by reference inits entirety.

SUMMARY OF THE INVENTION

OLED devices and method of fabricating the same are provided. Thedevices include emissive regions and locally-transparent regions, suchthat the device has an overall transparency of at least 5%.

In an embodiment of the invention disclosed herein, a device may includea light emitting surface a first region and a second region, where thedevice transmits light through the first region and emits light from thesecond region, and has an overall device transparency of at least 5%, atleast 10%, or more. The device may be, for example, a display such as afull-color display, an OLED display, an AMOLED display, a flexible OLEDdisplay, or the like. The second region may have a higher localtransparency than the first region, for example where the localtransparency of the region is less than 5%, less than 1%, or less. Thedevice may include multiple OLEDs configured to emit light through thefirst surface, which may be arranged to emit light only or primarilythrough the first region of the light emitting surface. The OLEDs mayoccupy not more than about 75% of the total area of the display. Atleast 70% of the area of the display not occupied by the plurality ofOLEDs may have a local transparency of at least 25%, 50%, or more. Thedevice may be divided into regions, each of which includes at least oneOLED and a transparent region having a local transparency of at least25%. Overall, such transparent regions may occupy at least 25% of thetotal area of the light emitting surface. In some configurations theOLED devices may include a white emitting device and/or one or morecolor filters. The device may be flexible, and may be fabricated on, forexample, a plastic substrate. It also may include additional layers,such as protective layers, including a single layer barrierencapsulation layer, which may be disposed over the light emittingsurface or another surface of the device.

In an embodiment of the invention disclosed herein, an OLED device mayinclude two electrodes having different surface areas, where the surfacearea of one is not more than about 80% of the surface area of the other,and an emissive layer disposed between the electrodes. The OLED devicemay be configured to emit light only through one electrode.Alternatively or in addition, multiple electrodes may be disposed on oneside of the emissive layer, which have a combined surface area of notmore than about 80% of the surface area of the other electrode. Thedevice may have an overall transparency of at least 5%, 10%, or more. Itmay include an OLED, an AMOLED, a flexible OLED, one or more colorfilters or filter layers, a flexible substrate such as a plasticsubstrate, a protective layer such as a single layer barrierencapsulation, or the like.

In an embodiment of the invention, a method of fabricating a device asdisclosed herein is provided. The method may include, for example,depositing an anode material over a substrate having a transparency ofat least 5%, to form a patterned layer that covers a first portion ofthe substrate and does not cover a second portion of the substrate,depositing an emissive layer over the first portion and the secondportion of the substrate, and depositing a cathode material over thefirst portion and the second portion of the substrate. Such a methodalso may use appropriate substrates, emissive layers, controlcomponents, and other components as disclosed herein. The resultingdevice may have an overall transparency of 5%, 10%, or more.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows an organic light emitting device.

FIG. 2 shows an inverted organic light emitting device that does nothave a separate electron transport layer.

FIG. 3 shows a schematic top view of a region of an example deviceaccording to an embodiment of the invention.

FIG. 4A shows an example arrangement of emissive and transparent regionsaccording to an embodiment of the invention, in which the emissiveregions have non-equal areas the transparent region is contiguous.

FIG. 4B shows an example arrangement of emissive and transparent regionsaccording to an embodiment of the invention, in which the transparentregion is non-contiguous.

FIG. 4C shows an example arrangement of emissive and transparent regionsaccording to an embodiment of the invention that includes two emissiveregions separated by a transparent region.

FIG. 4D shows an example arrangement of emissive and transparent regionsaccording to an embodiment of the invention that includes anon-contiguous transparent region and emissive regions with non-equalareas.

FIG. 5 shows an example device according to an embodiment of theinvention that includes multiple emissive regions and a transparentregion that surrounds the emissive regions.

FIG. 6 shows an example of a device according to an embodiment of theinvention that includes two electrodes, where one has a surface arealess than the surface area of the other.

FIG. 7 shows an example of a device according to an embodiment of theinvention that includes multiple electrodes, where the combinedelectrode surface area on one side of the device is less than thesurface area of a single electrode on the other side of the device.

FIG. 8 shows an example device according to an embodiment of theinvention in which an emissive layer is disposed over a non-transparentelectrode.

DETAILED DESCRIPTION

Generally, an OLED comprises at least one organic layer disposed betweenand electrically connected to an anode and a cathode. When a current isapplied, the anode injects holes and the cathode injects electrons intothe organic layer(s). The injected holes and electrons each migratetoward the oppositely charged electrode. When an electron and holelocalize on the same molecule, an “exciton,” which is a localizedelectron-hole pair having an excited energy state, is formed. Light isemitted when the exciton relaxes via a photoemissive mechanism. In somecases, the exciton may be localized on an excimer or an exciplex.Non-radiative mechanisms, such as thermal relaxation, may also occur,but are generally considered undesirable.

The initial OLEDs used emissive molecules that emitted light from theirsinglet states (“fluorescence”) as disclosed, for example, in U.S. Pat.No. 4,769,292, which is incorporated by reference in its entirety.Fluorescent emission generally occurs in a time frame of less than 10nanoseconds.

More recently, OLEDs having emissive materials that emit light fromtriplet states (“phosphorescence”) have been demonstrated. Baldo et al.,“Highly Efficient Phosphorescent Emission from OrganicElectroluminescent Devices,” Nature, vol. 395, 151-154, 1998;(“Baldo-I”) and Baldo et al., “Very high-efficiency green organiclight-emitting devices based on electrophosphorescence,” Appl. Phys.Lett., vol. 75, No. 3, 4-6 (1999) (“Baldo-II”), which are incorporatedby reference in their entireties. Phosphorescence is described in moredetail in U.S. Pat. No. 7,279,704 at cols. 5-6, which are incorporatedby reference.

FIG. 1 shows an organic light emitting device 100. The figures are notnecessarily drawn to scale. Device 100 may include a substrate 110, ananode 115, a hole injection layer 120, a hole transport layer 125, anelectron blocking layer 130, an emissive layer 135, a hole blockinglayer 140, an electron transport layer 145, an electron injection layer150, a protective layer 155, a cathode 160, and a barrier layer 170.Cathode 160 is a compound cathode having a first conductive layer 162and a second conductive layer 164. Device 100 may be fabricated bydepositing the layers described, in order. The properties and functionsof these various layers, as well as example materials, are described inmore detail in U.S. Pat. No. 7,279,704 at cols. 6-10, which areincorporated by reference.

More examples for each of these layers are available. For example, aflexible and transparent substrate-anode combination is disclosed inU.S. Pat. No. 5,844,363, which is incorporated by reference in itsentirety. An example of a p-doped hole transport layer is m-MTDATA dopedwith F₄-TCNQ at a molar ratio of 50:1, as disclosed in U.S. PatentApplication Publication No. 2003/0230980, which is incorporated byreference in its entirety. Examples of emissive and host materials aredisclosed in U.S. Pat. No. 6,303,238 to Thompson et al., which isincorporated by reference in its entirety. An example of an n-dopedelectron transport layer is BPhen doped with Li at a molar ratio of 1:1,as disclosed in U.S. Patent Application Publication No. 2003/0230980,which is incorporated by reference in its entirety. U.S. Pat. Nos.5,703,436 and 5,707,745, which are incorporated by reference in theirentireties, disclose examples of cathodes including compound cathodeshaving a thin layer of metal such as Mg:Ag with an overlyingtransparent, electrically-conductive, sputter-deposited ITO layer. Thetheory and use of blocking layers is described in more detail in U.S.Pat. No. 6,097,147 and U.S. Patent Application Publication No.2003/0230980, which are incorporated by reference in their entireties.Examples of injection layers are provided in U.S. Patent ApplicationPublication No. 2004/0174116, which is incorporated by reference in itsentirety. A description of protective layers may be found in U.S. PatentApplication Publication No. 2004/0174116, which is incorporated byreference in its entirety.

FIG. 2 shows an inverted OLED 200. The device includes a substrate 210,a cathode 215, an emissive layer 220, a hole transport layer 225, and ananode 230. Device 200 may be fabricated by depositing the layersdescribed, in order. Because the most common OLED configuration has acathode disposed over the anode, and device 200 has cathode 215 disposedunder anode 230, device 200 may be referred to as an “inverted” OLED.Materials similar to those described with respect to device 100 may beused in the corresponding layers of device 200. FIG. 2 provides oneexample of how some layers may be omitted from the structure of device100.

The simple layered structure illustrated in FIGS. 1 and 2 is provided byway of non-limiting example, and it is understood that embodiments ofthe invention may be used in connection with a wide variety of otherstructures. The specific materials and structures described areexemplary in nature, and other materials and structures may be used.Functional OLEDs may be achieved by combining the various layersdescribed in different ways, or layers may be omitted entirely, based ondesign, performance, and cost factors. Other layers not specificallydescribed may also be included. Materials other than those specificallydescribed may be used. Although many of the examples provided hereindescribe various layers as comprising a single material, it isunderstood that combinations of materials, such as a mixture of host anddopant, or more generally a mixture, may be used. Also, the layers mayhave various sublayers. The names given to the various layers herein arenot intended to be strictly limiting. For example, in device 200, holetransport layer 225 transports holes and injects holes into emissivelayer 220, and may be described as a hole transport layer or a holeinjection layer. In one embodiment, an OLED may be described as havingan “organic layer” disposed between a cathode and an anode. This organiclayer may comprise a single layer, or may further comprise multiplelayers of different organic materials as described, for example, withrespect to FIGS. 1 and 2 .

Structures and materials not specifically described may also be used,such as OLEDs comprised of polymeric materials (PLEDs) such as disclosedin U.S. Pat. No. 5,247,190 to Friend et al., which is incorporated byreference in its entirety. By way of further example, OLEDs having asingle organic layer may be used. OLEDs may be stacked, for example asdescribed in U.S. Pat. No. 5,707,745 to Forrest et al, which isincorporated by reference in its entirety. The OLED structure maydeviate from the simple layered structure illustrated in FIGS. 1 and 2 .For example, the substrate may include an angled reflective surface toimprove out-coupling, such as a mesa structure as described in U.S. Pat.No. 6,091,195 to Forrest et al., and/or a pit structure as described inU.S. Pat. No. 5,834,893 to Bulovic et al., which are incorporated byreference in their entireties.

Unless otherwise specified, any of the layers of the various embodimentsmay be deposited by any suitable method. For the organic layers,preferred methods include thermal evaporation, ink-jet, such asdescribed in U.S. Pat. Nos. 6,013,982 and 6,087,196, which areincorporated by reference in their entireties, organic vapor phasedeposition (OVPD), such as described in U.S. Pat. No. 6,337,102 toForrest et al., which is incorporated by reference in its entirety, anddeposition by organic vapor jet printing (OVJP), such as described inU.S. Pat. No. 7,431,968, which is incorporated by reference in itsentirety. Other suitable deposition methods include spin coating andother solution based processes. Solution based processes are preferablycarried out in nitrogen or an inert atmosphere. For the other layers,preferred methods include thermal evaporation. Preferred patterningmethods include deposition through a mask, cold welding such asdescribed in U.S. Pat. Nos. 6,294,398 and 6,468,819, which areincorporated by reference in their entireties, and patterning associatedwith some of the deposition methods such as ink-jet and OVJD. Othermethods may also be used. The materials to be deposited may be modifiedto make them compatible with a particular deposition method. Forexample, substituents such as alkyl and aryl groups, branched orunbranched, and preferably containing at least 3 carbons, may be used insmall molecules to enhance their ability to undergo solution processing.Substituents having 20 carbons or more may be used, and 3-20 carbons isa preferred range. Materials with asymmetric structures may have bettersolution processability than those having symmetric structures, becauseasymmetric materials may have a lower tendency to recrystallize.Dendrimer substituents may be used to enhance the ability of smallmolecules to undergo solution processing.

Devices fabricated in accordance with embodiments of the presentinvention may further optionally comprise a barrier layer. One purposeof the barrier layer is to protect the electrodes and organic layersfrom damaging exposure to harmful species in the environment includingmoisture, vapor and/or gases, etc. The barrier layer may be depositedover, under or next to a substrate, an electrode, or over any otherparts of a device including an edge. The barrier layer may comprise asingle layer, or multiple layers. The barrier layer may be formed byvarious known chemical vapor deposition techniques and may includecompositions having a single phase as well as compositions havingmultiple phases. Any suitable material or combination of materials maybe used for the barrier layer. The barrier layer may incorporate aninorganic or an organic compound or both. The preferred barrier layercomprises a mixture of a polymeric material and a non-polymeric materialas described in U.S. Pat. No. 7,968,146, PCT Pat. Application Nos.PCT/US2007/023098 and PCT/US2009/042829, which are herein incorporatedby reference in their entireties. To be considered a “mixture”, theaforesaid polymeric and non-polymeric materials comprising the barrierlayer should be deposited under the same reaction conditions and/or atthe same time. The weight ratio of polymeric to non-polymeric materialmay be in the range of 95:5 to 5:95. The polymeric material and thenon-polymeric material may be created from the same precursor material.In one example, the mixture of a polymeric material and a non-polymericmaterial consists essentially of polymeric silicon and inorganicsilicon.

Devices fabricated in accordance with embodiments of the invention maybe incorporated into a wide variety of consumer products, including flatpanel displays, computer monitors, medical monitors, televisions,billboards, lights for interior or exterior illumination and/orsignaling, heads up displays, fully transparent displays, flexibledisplays, laser printers, telephones, cell phones, personal digitalassistants (PDAs), laptop computers, digital cameras, camcorders,viewfinders, micro-displays, vehicles, a large area wall, theater orstadium screen, or a sign. Various control mechanisms may be used tocontrol devices fabricated in accordance with the present invention,including passive matrix and active matrix. Many of the devices areintended for use in a temperature range comfortable to humans, such as18 degrees C. to 30 degrees C., and more preferably at room temperature(20-25 degrees C.).

The materials and structures described herein may have applications indevices other than OLEDs. For example, other optoelectronic devices suchas organic solar cells and organic photodetectors may employ thematerials and structures. More generally, organic devices, such asorganic transistors, may employ the materials and structures.

The terms halo, halogen, alkyl, cycloalkyl, alkenyl, alkynyl, arylkyl,heterocyclic group, aryl, aromatic group, and heteroaryl are known tothe art, and are defined in U.S. Pat. No. 7,279,704 at cols. 31-32,which are incorporated herein by reference.

In a conventional OLED display, it is common to try to maximize the fillfactor or pixel aperture ratio, that is, the fraction of display surfaceor pixel-covered area that emits light. This typically may reduce thecurrent density required to be applied to the active OLED devices toachieve a desired performance, and thus extend device lifetimes.

Transparent OLEDs (TOLEDs) have been demonstrated where the basic OLEDdevice is effectively transparent, and which emit light through both theanode and cathode surfaces. Such devices typically may be constructed byusing a transparent cathode combined with the commonly used transparentanode. Conventional TOLED displays also may use semi-transparentcathodes, which can be more difficult than metal cathodes to make inmass production as they may rely on a relatively high uniformity of thinfilms used during fabrication.

In some cases it may be desirable to use a TOLED that emits light inonly one direction, while the overall display remains relativelytransparent or partially transparent. Various TOLED arrangements havebeen demonstrated that emit only in one direction by using filters orpolarized light and/or polarizers, for example on one surface of thedevice. Such devices also may be relatively complex and costly toconstruct, and may have a relatively low overall transparency and/orrelatively high thickness.

In an embodiment of the invention, a transparent organic light emittingdevice is provided. The OLED device may include an anode, a cathode, andan organic emissive layer disposed between the anode and the cathode.The organic emissive layer may include a host and a phosphorescentdopant or any other combination of emissive and other materials aspreviously described herein. The device may also include one or morelocally transparent regions, which allows the device to have an overalltransparency of 5% or more.

Generally, a device as disclosed herein includes one or more emissiveregions adjacent to one or more transparent regions. For example, for afull color display, the device may include red, green, and blue OLEDs,such as conventional bottom- or top-emission OLED devices, which are notconventional transparent OLED devices. The emissive OLED devices may bedisposed adjacent to one or more regions that have a relatively highdegree of transparency, and which may not contain a metallicnon-transparent electrode. Devices disclosed herein also may beconstructed to emit white light, or to emit monochrome or any othersubset of color compared to a full-color display. Similarly, instead ofusing red, green, and blue emissive regions, devices as disclosed hereinmay use white emissive devices in conjunction with color filters toachieve visible light of a desired color. OLED devices as disclosedherein include emissive regions with electrodes that are opaque oressentially opaque and therefore prevent transmission through thedevice, and only emit light through one surface of the OLED devices.When these emissive devices are disposed adjacent to transparent regionsthat allow transmission through the device, the device may appeartransparent when viewed by the human eye while only emitting light in asingle direction. For example, a display may be transparent to visiblelight, while emitting light through a single surface of the display. Insome cases, OLEDs and similar devices may emit a relatively small amountof light in directions other than the primary emissive surface orsurfaces, such as where a small amount of light may be emitted from theedges of the device. Such light typically may be blocked or masked by,for example, a housing or other component. As used herein, a device isconsidered to emit light through a single surface or in a singledirection if 97%, more preferably 98%, and more preferably 99% of lightemitted by the device is emitted through the single surface or in thesingle direction.

Devices as disclosed herein may be implemented using, for example, atypically metallic cathode deposited through a mask so as not to bedisposed over the locally-transparent regions for a bottom-emissivedevice. As another example, for a top emission device, where the anodeis usually reflective, the anode may be patterned so as not to blocklight through the locally-transparent region or regions. The emissiveregions may be driven in any suitable conventional manner, such as usingrow and column drivers, whereas the locally-transparent region may notbe electrically driven.

FIG. 3 shows a schematic top view of a region of an example deviceaccording to an embodiment of the invention. The region shown may be,for example, a portion of a full-color display or other emissive device,such as a general purpose lighting device. The region includes one ormore emissive regions 310, 320, 330, which may be red, green, and blueemissive elements, respectively. A second region 340 may be non-emissivebut relatively transparent. More specifically, the emissive region orregions 310, 320, 330 may be more opaque than the transparent region340, such that light is prevented from being transmitted through thedevice in the emissive regions, but may pass through the transparentregion 340. The region and/or the device as a whole may have an overalltransparency of at least 5%, at least 10%, or more. That is, at least 5%or more of the light that is incident on either side of the device maybe transmitted through the device. The emissive regions 310, 320, 330prevent light from being transmitted through the device, but emit lightthrough one surface of the device. As used herein, a surface of a devicethrough which light emitted by components of the device is emitted maybe referred to as a “light emitting” surface, though the light may begenerated by components other than the device such as OLEDs or otheremissive components within the device. That is, a “light emitting”surface of a device may not itself be emissive, but may allow lightgenerated within the device to be transmitted through the device to aregion external to the device.

The emissive regions 310, 320, 330 may be OLEDs, including AMOLEDs, asdescribed herein. Each region may include a separate OLED, such as whereeach region is configured to emit a different color of light.Preferably, each OLED is configured to emit light primarily, essentiallyentirely, or entirely through a single surface of the device. Forexample, where the device is a full-color flat panel display, the OLEDsmay emit light only through the display surface, and not emit lightthrough the back surface of the device. In some configurations, arelatively small amount of light may be emitted through the sides of thedevice, i.e., parallel to the plane of the device.

By adjusting the relative areas of the device that include emissiveregions and transparent regions and the transparency of each transparentregion, a desired overall transparency may be achieved. For example, atransparent region may have a local transparency of at least 25%, 50%,or more. As used herein, a “local transparency” refers to thetransparency of only the transparent region considered alone, withoutregard to the transparency of any other region of the device or thedevice as a whole. Thus, a region having a local transparency of 25%allows about 25% of incident light to be transmitted through the device,though when considered as a whole the device may allow about 5% or 10%of incident light to be transmitted through the device. The transparencyof a device or a region may be determined by measuring the luminosity ofvisible light incident on the device and the resulting luminosity oflight transmitted through the device or region. Since the emissiveregions are opaque, a greater area of the device that includes emissiveregions leads to a lower overall transparency for the device. In anembodiment, it may be preferred for the emissive regions to extend overnot more than about 75% of the total area of the device. This may behigher than conventional displays due to the area usually required byother parts of the pixel that may not be transparent, such as bus lines,TFTs, and the like. Thus, it also may be useful to determine the areathat includes emissive regions relative to the area available foremissive regions such as OLEDs in the device, when other components areexcluded. In an embodiment, it may be preferred for the emissive regionsto occupy at least about 20% of the area available for emissivecomponents in a device such as a display.

Such a configuration allows for an overall transparency of the region ordevice of at least 5%. Similarly, the greater the area of thetransparent region, the greater the overall transparency of the deviceor region. In an embodiment, it may be preferred for the area notoccupied by the emissive region or regions to have a local transparencyof at least 25%, 50%, or more. In some configurations, portions of thedevice that do not include emissive regions also may not be transparent,or may be less transparent than the transparent regions. For example,the device may include a housing, structural supports, circuitry, orother layers or components that are less transparent that the layers andmaterials in the transparent regions. In an embodiment, at least 70%,80%, 90%, or more of the area not occupied by an emissive region mayhave a local transparency of 25%, 50%, or more. Alternatively or inaddition, it may be preferred for transparent regions in the device tooccupy at least 10% of the total area of the device.

Although described with respect to FIG. 3 as using individual OLEDs ofdifferent colors, the configurations disclosed herein also may be usedto realize to white-emitting devices that may or may not include a colorfilter layer disposed over each emissive region or OLED. For example,each of the emissive regions 310, 320, 330 in FIG. 3 may be awhite-emitting device, or fewer larger devices may be used. One or morecolor filters may be disposed between the white-emitting devices and theemissive surface of the device to allow for a colored or full-colordisplay.

As previously described, a variety of substrates and other layers may beused with any embodiment of the invention. For example, a plastic and/orflexible substrate may be used. Flexible and plastic substrates aredisclosed herein, and are also described in further detail in U.S. Pat.No. 6,664,173, the disclosure of which is incorporated by reference inits entirety. Similarly, a single layer barrier as disclosed herein maybe used as an encapsulation layer of the device.

FIG. 3 shows an example arrangement of emissive regions and atransparent region. FIGS. 4A-4D show additional examples of sucharrangements in accordance with the invention. Notably, a deviceaccording to the invention, or a region of such a device, need not havea single contiguous transparent region. Further, the emissive regionsneed not be immediately adjacent to one another, and need not have equalareas. FIG. 4A shows an example arrangement in which the emissiveregions 310, 320, 330 have non-equal areas and in which the transparentregion 340 is contiguous. FIG. 4B shows an example arrangement in whichthe transparent region 340 is non-contiguous. FIG. 4C shows an examplearrangement that includes two emissive regions 310, 320 separated by atransparent region 340. FIG. 4D shows an example arrangement with anon-contiguous transparent region and emissive regions 310, 320, 330with non-equal areas. As is understood in the art, arrangements such asthose shown in FIGS. 4A-4D may be used, for example, to adjust therelative emission of differently-colored OLED devices, such as toachieve an overall improved lifetime.

FIGS. 3 and 4A-4D show example regions of a device. As will be readilyunderstood by one of skill in the art, these arrangements may beextended to a larger-scale device, such as a general illumination panel,a limited- or full-color display, or the like. FIG. 5 shows an exampledevice having multiple emissive regions 510 and a transparent region 520that surrounds the emissive regions 510. It will be apparent that, byselecting various regions of the larger region shown in FIG. 5 ,arrangement such as those described with respect to FIGS. 3 and 4A-4Dmay be identified. For example, the region 531 includes six emissiveregions surrounded by a contiguous transparent region. Similarly, theregion 532 includes three emissive regions a non-contiguous transparentregion.

The emissive regions described with respect to FIGS. 3-5 may compriseone or more OLEDs having various arrangements, and may be fabricated ina variety of ways. In an embodiment, each emissive region may include anOLED, such as an AMOLED. FIG. 6 shows an example of such an OLED 600.The device includes an electrode 610, an emissive layer 620, and anelectrode 630 with a surface area less than the surface area of theelectrode 610. It may be preferred for the electrode 630 to have asurface area that is not more than about 80% the surface area of theelectrode 610. Although FIG. 6 shows an example device having only anemissive layer for ease of illustration, it will be understood that thedevice may include any of the other layers conventionally used in anOLED, such as the layers described with respect to FIGS. 1 and 2 .Further, the device may include additional emissive layers, and may emita combination of colors or white light. As previously described, thedevice also may include color filters to allow operation as a white andcolored or full-color device. It also may include a single-layer barrieras an encapsulation layer, as well as other suitable coverings, layers,components, and the like.

In operation, the device 600 may emit light from the region of theemissive layer 620 that is disposed between the electrodes 610 and 630.The emissive layer 620, the electrode 610, and other layers disposedbetween the electrodes 610, 630 may be transparent, preferably at least25% transparent, while the electrode 630 may be completely or relativelyopaque. For example, the electrode 630 may be less than 5% transparent.Thus, an arrangement such as shown in FIG. 6 may provide both anemissive region 601 and a transparent region 602, which may correspondto an emissive region and a transparent region as described with respectto FIGS. 3-5 , respectively. In configurations in which electrode 630 isfully opaque, light may be emitted only through the bottom electrode 610because the emissive OLED will only be formed in the region defined bythe overlap of the two electrodes 610 and 630.

FIG. 7 shows a configuration similar to the configuration shown in FIG.6 , that includes multiple electrodes 630, 710 that have a combinedsurface area less than that of the electrode 610. Such a configurationprovides multiple emissive regions 701, 703 and a transparent region702. The electrodes 630, 710 may be deposited and patterned using any ofthe patterning techniques disclosed herein.

FIG. 8 shows an example configuration in which the emissive layer 620 isdisposed over the non-transparent electrode 630. As previouslydescribed, such a configuration may provide an emissive region 601 and atransparent region 602.

The OLED device arrangements shown in FIGS. 6-8 may be top-emitting orbottom-emitting devices. That is, they may be configured to emit lightthrough only the electrode 610, such as in configurations where theelectrode 630 is opaque. As previously described, the device 600 mayhave an overall transparency of at least 5%, at least 10%, or more,since it includes both a transparent region and one or morenon-transparent devices. The layers shown in FIGS. 6-8 may be disposedover any suitable substrate, such as flexible substrates, plasticsubstrates, and the like, as previously described.

Other configurations may be used to achieve a device having bothemissive regions or devices and transparent regions as described. Forexample, each emissive region may be an individual OLED that isphysically separated from some or all of adjacent OLEDs. The OLEDs maybe disposed on or within additional transparent layers, such as asubstrate, an encapsulation layer, an active or passive backplane, andthe like. The additional layers may be at least 5% transparent, thusproviding the transparent regions previously described in those regionsthat do not include an OLED.

Devices as disclosed herein may be fabricated in a variety of ways. Forexample, referring to FIGS. 6 and 7 , the electrode 610, emissive layer620, and other layers in the device may be deposited using any of theappropriate techniques disclosed herein. The electrode 630 and 710 (ifpresent) may then be deposited over the electrode 610, emissive layer620, and any other intervening layers, using a mask or other patterningdeposition technique. Similarly, referring to FIG. 8 , an electrodematerial, such as an anode material, may be deposited on a substrate toform the electrode 630, such that the deposited material covers only aportion of the substrate. The emissive layer 620, electrode 610, andother intervening layers may be deposited over the same portion of thesubstrate, as well as at least a portion of the substrate over which theelectrode material 630 is not deposited. As previously described, theelectrode 610, emissive layer 620, and other layers may be at least 5%transparent or more, thus allowing the region of the completed devicethat is not disposed over the electrode 630 to be at least 5%transparent.

It is understood that the various embodiments described herein are byway of example only, and are not intended to limit the scope of theinvention. For example, many of the materials and structures describedherein may be substituted with other materials and structures withoutdeviating from the spirit of the invention. The present invention asclaimed may therefore include variations from the particular examplesand preferred embodiments described herein, as will be apparent to oneof skill in the art. It is understood that various theories as to whythe invention works are not intended to be limiting.

1. A device comprising: a first plurality of top-emitting organic lightemitting diodes (OLEDs) that are disposed over a transparent substrate;and a second plurality of bottom-emitting OLEDs that are disposed overthe transparent substrate, wherein the device has an overalltransparency of at least 5%.
 2. The device of claim 1, wherein one ormore of the first plurality of top-emitting OLEDs and the secondplurality of bottom-emitting OLEDs includes a phosphorescent dopant. 3.The device of claim 1, wherein one or more of the first plurality oftop-emitting OLEDs and the second plurality of bottom-emitting OLEDs isphosphorescent.
 4. The device of claim 1, wherein at least one of thefirst plurality of top-emitting OLEDs is disposed at least partiallyover at least one of the second plurality of bottom-emitting OLEDs. 5.The device of claim 1, wherein at least one of the first plurality oftop-emitting OLEDs and the second plurality of bottom-emitting OLEDs areconfigured to emit light through a first region of the transparentsubstrate.
 6. The device of claim 1, further comprising: at least oneadditional layer selected from the group consisting of: a color filter,a single-layer barrier as an encapsulation layer, an active backplane,and a passive backplane disposed on or under at least one of the firstplurality of top-emitting OLEDs and the second plurality ofbottom-emitting OLEDs.
 7. The device of claim 1, wherein the device hasan overall transparency of at least 10%.